Parameter and heat transfer performance evaluation of an existing dryer mixer for “Irvingia gabonensis” powder

Abstract

A homogeneous mixing and drying of food substance are required prior to further processing and storage. This research was carried out to determine the heat transfer parameters of an existing dryer-mixer and evaluate its performance for the drying and mixing of Irvingia gabonensis powder. A 1 kg of the powdered product (~ 15 μm particle size and 24.5% initial moisture content) was dried using the mixer-dryer for 5 hours. The average temperature of the drying chamber was preset at 50oC for the drying process,with the help of a thermostat. The heat transfer parameters, which includes the air flow rate and thickness of wall lagging, were determined mechanistically. Also, the drying performance was determined based on the drying rate, drying efficiency, mixing index, and mixing rate of the machine. Results show that an air flow rate of 0.00082 kgs-1and 0.02 m thickness of a fibre-glass lagging material was required in the drying and mixing operation. Energy required to dry the product from 24.5% (wb) to 12.8% (wb) moisture content was 0.08514 kJ/s at a drying rate of 1.8 kgh-1. A mixing index of 0.819 and efficiency of 82.2 % were obtained, and these may imply effective drying and a high degree of homogenization in the system.

Keywords

• energy
• air flow rate
• design
• thermal conductivity
• performance